Telephone system



Oct. 23, 1928.

W. O. PASSMORE TELEPHONE SYSTEM Filed July 6, 1926 2 Sheets-Sheet l Inuen or Milliam Elegy Fassmure W. O. PASSMORE TELEPHONE SYSTEM Oc t. 23, 1928.

Filed July 6, 1926 2 Sheets-Sheet 2 sl Aim F lumen UP Milliam P13153119 Passmur:

Patented on. 23, 1928.

UNITED STATES 1,688,651 PATENT OFFICE WILLIAM OGLESBY PASSMORE, OF LIVERPOOL, ENGLAND, ASSIGNOR TO AUTOMATIC ELECTRIC 13510., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAVIAEE.

TELEPHONE SYSTEM.

Application filed July 6, 1926, Serial No. 120,735, and in Great Britain July 20, 1925.

This invention relates to automatic or semiautomatic telephone systems and is particularly concerned with such systems in which talking current is supplied from the trunking switch (selector) rather than from a final selector (connector) and one object of the invention is the production of new and improved circuit arrangements t'or such selectors, intermediate selectors and connectors whereby the number of relays in these switches may be considerably reduced.

A further object of the present invention concerns the provision of new and improved circuit arrangements for transmitting busy signalling currents and metering currents in a system of the above character. 7

Referring now to the drawings comprising Figs. 13, they show by means of usual circuit diagrams so much of the equipment in a telephone system embodying the features 01": the invention as is necessary for the invention to be understood. Specifically, Fig. 1 shows a first selector repeater; Fig. 2 shows an intermediate selector accessible to the first selector repeater of Fig. 1; and Fig. 3 shows a connector'accessible to the intermediate selector of Fig. 2.

According to the present invention a group of relays associated with a first selector switch is arranged to feed talking current to both the calling and called subscribers, guarding po tential being ted forward to hold up all local switches taken into use. On all connections the battery teed selector is arranged to function as a selector repeater. The impulsing circuit of this battery feed selector is arranged so that the relay which responds to impulses generated by a calling party repeats the first series directly to the magnet of the first seiector. while subsequent impulses for setting local switches are controlled over one speaking conductor and subsequent impulses for controlling switches in distant exchanges are transmitted over both sides of a two-wire junction in series. After each series of impulses to local switches the relay group is arranged to exert a controlling efiect over the other speaking conductor for the hunting magnets of the series. The change over from the one wire impulsing circuit to the two wire circuit is brought about by a device which is energized when the selector is set to a level having access to junction lines. Preterably the device is energized over an addi tional Wiper, the bank contacts engaged by this wiper being earthed on any one or a number of levels as desired. Instead of earthing the bank contacts engaged by the additional wiper at the first selector they may be earthed at a second or subsequent selector. By this means great flexibility is attained as it is possible to have outgoing trunks on any level or levels of the first or intermediate selectors. Where this flexibility is not required the additional wiper may be eliminated by operating the device on a certain level or levels of the first selector by normal post or level sprmgs. tors are considerably simplified by having only two relays, one serving to control switching and rel-ease functions and the other the automatic hunting operation. The impulse relay in the battery feed selector transmits impulses direct to the operating magnets of the intermediate local selectors over the negative speaking conductor and the relay in the battery feed selector which de-energizes at the end of each series of impulses controls the hunting op-erationoftheintermediateselectors over the positive speaking conductor. The combined switching and release relay of the intermediate selectors is arranged to be partially energizedover the release trunk conductor by guardingpotential fed forward from the battery feed selector and to disconnect the release magnet of the intermediate selectors.

In the connector switch only four relays are required a release relay energized by guarding potential fed forward over the release trunk'conductor, a change overrelay energized in turn in series with the vertical and rotary magnets, acombined busy and ring-cut off relay and a switching relay. The impulses for operating the vertical and rotary magnets of the connector are transmitted over one speaking conductor from the battery feed selector. In order to take care of certain supervisory arrangements, the battery feed selector is provided with a busy relay, a high impedance relay and a polarized relay. The high impedance relay is arranged to be normally connected between earth and the positive speaking conductor so that it can be energized by connecting battery to the positive speaking conductor for example at an operators position. The energization of the high impedance relay under these conditions is arranged to place the release of the switches under the control ot the o erators position The second and intermediate selecsince when the high impedance relay is encrgized alone the guarding potential for holding up all the switches is controlled by this relay. The busy relay in the battery feed selector is normally connected between battery and the negative speaking conductor so that the high impedance relay and the busy relay may be operated over both speaking conductors in series to control the calling partys meter, the meter being actuated either by a reversal or booster battery as desired. This busy relay may also be operated alone by conn-wting earth to the negative speaking conductor. When the busy relay is energized alone it is arranged to connect a busy signalling conductor to the positive speaking conduct-or ot the calling line. This busy signalling conductor is connected to a busy tone current and battery and a busy tone current and earth alternately.

When the battery teed selector is set to a .level having access to junction lines, a relay is operated which changes the connections of the high impedance re .y so that it is now connected in series with a polarized relay and across the speaking conductors. llhis change over relay also ciisc'onnects the busy relay. The circuit for transmitting the busy flash or/and tone current is new controlled by the high impedance relay over the out going loop circuit. Metering over junction lines is eii'ectedby the polarized relay which responds to a reversal of current over the junction line.

Should all the lines accessible through the called level of the battery "t ed selector be busy, the Wipers will be stepped on to the 11th contact whereup 11th step cam springs will operate and connectv guarding potential to the release trunk, disconnect the vertical. magnet in order to prevent further operation of the switch should the calling party con tinue to dial, complete a local circuit for the busy relay which thereupon operates and connects busy tone and battery to the calling partys line, the switch being released by the calling party hanging up his receiver and bringing about the release or the line relay.

Should all the trunks accessible to an intermediate selector be engaged, the 11th. step cam springs disconnect the vertical magnet andconnect earth to the negative speaking conductor which completes a circuit for the busy relay. The busy relay also removes guarding potential from the release trunk thereby allowing a marginally adjusted switching relay in the second selector to deenergize and complete a circuit for the re lease magnet and thus restore the SOCOIlt. see lector to normal. It should be understood that while the foregoing descriptioncontemplates operating the driving magnets of the local selectors and connectors direct from the battery teed selector over one off the speaking conductors that an impulse relay may be inserted to control the driving magnets locally if desired.

A description will first be given of the manner in which a local call is set up. Assuming that the battery feed selector repeater, Fig.

l, is taken into use by a calling party, the impulsing relay A energizes overthe positive and negative leads and completes a circuit at armature l for the slow release relay B. Relay B upon energizing earths the release trunk RT at armature t; at armature 5 pre pares the impulsing circuit for the vertical magnet V. Bela it responds to impulses dialled by the calling party and repeats them to the vertical magnet over the following circuit: earth, 1, 35, 5, C, 1 1', 39, CS), V, battery. Relay 0 energizes in series with the vertical magnet V and operates its armatures 6, 7, 8, 9, l0 and 11 and being slow to release remains energized throughout the series of impulses. -The vertical magnetre sponds to the series of impulses and raisesits wipers to level in accordance with the impulses transmitted. Upon the first vertical step, the oil normal springs l and Nf close. The closure of oil normal springs N with relay C in operated position completes a circuit for stepping relay E: battery, E, N, contacts oi R, 38, 8, 25, 4-, earth. Relay E upon energizing establishes a locking circuit for itself at armature 21 and at armature 22 prepares the circuit for the rotary magnet R.

1. t the end of the series of impulses, relay C ole-energizes and at the normally closed contacts controlled by armature 8 completes the following circuit for the rotary magnet 1%: battery, R, 22, contacts controlled by 8, 25, i, earth. the rotary magnet upon energizing advances its wipers into engagement with the first setojf bank contacts in the selected level and at its interrupter contacts et2, breaks the locking circuit for stepping relay E, which accordingly ale-energizes. g

It the first trunk in the selected level'is busy, test wiper 3? will be earthed and relay E will be energized over the "following cir-' engaged, the switch wipers will be automatically stepped on to the 11th contact when the following circuit will be complete by the 7 operation of the 11th step cam springs CS, CS and CS By the operation of cam springs CS earth at armature 3 is connected to test wiper p in order to operate an overflow meter (not shown) which indicatesthe number of times lili the calling partys impulse sender from actuating the switch, and by the operation of cam springs CS the following circuit is completed for slow relay F battery, lower winding of relay F, 43, 26, CS 25, 4, earth. Relay F upon energizing completes the following circuit for itself at armature 28 battery, upper winding of relay F, 28, 44, 4, earth: and at armature 47 connects the combined i11- termittent busy tone and busy flash conductor IE to the calling partys positive speaking conductor as follows: 1B, 13, 29, 4'7, positive speaking conductor. The battery feed selector is held in this busy condition until the calling party hangs up and releases the impulsing relay A to release the switch by operating the release magnet Z.

When an idle trunk is found, no earth will be present on the test conductor 39 and relay H will not be short circuited and will now energize in series with relay E. Relay E will not energize however in series with the high resistance relay H. Relay H upon energizing operates its armatures, 36, 37, 38, 39, and 41 and at armature 36 connects the positive wiper to the positive line of the second selector, Fig. 2, this line being used for the first automatic rotary step of the intermediate selectors; at armature 41 connects the negative wiper to the negative line of the second selector, this line being used for transmitting impulses for the vertical operation of the switches, and at armature 38 connects the test wiper p to the release trunk conductor RT, earth being fed forward over this conductor from the battery feed selector, Fig. 1 to guard the switches and control their release; at armature 37, relay H opens a point in the initial locking circuit of relay E; at armature 39 disconnects the vertical magnet V and at armature 40 disconnects the release magnet Z.

In the second or intermediate selector, Fig. 2, the earth on test wiper p completes a circuit for the upper winding of switching relay H which however only operates its armature 53 to open a point in the circuit of the release magnet Z. When the calling party dials the 118X- series of impulses, relay A in the battery feed selector repeats them to the vertical magnet V over the following circuit: earth, 1, 35, 5, C, 14, 39,15, 41, negative speaking conductor 57, CS V and battery. The vertical magnet V raises the wipers of the intermediate selector to the desired level and upon the first vertical step, the vertical oif normal springs l 2 and N close? The springs N prepare a circuit for stepping re lay E and the springs h 3 prepare a circuit for the release magnet Z.

At the end of the series of impulses, relay C in the battery feed selector ale-energizes and completes the following circuit for stepping relay E in the intermediate selector: earth, at armature 17 of relay Q, G, 9, 36, 6,

positive wiper, positive speaking conductor of the intermediate selector, Fig. 2', rotary oii' normal springs NR, 56, 52, vertical off normal springs N switching relay E, battery. Relay E completes a locking circuit for itself at armature and at armature 51 connects the rotary magnet R to the release trunk conductor RT. The rotary magnet energizes and steps the wipers on to the first set of contacts in the selected level. When the rotary magnet has fully energized, the rotary interrupter springs 52 open, breaking a circuit of relay E which d e-energizes. The rotary off normal springs NR are opened and the rotary off normal springs NR are closed; the springs NR prevent further control of relay E over the positive speaking conductor while the off normal springs NR connect up the lower winding of the switching relay H. Should the selected trunk be busy, relay E will be energized over the following circuit earth, on test wiper p 11th step cam springs CS 55, 52, N E and battery. The stepping relay E again operates and closes a circuit of the rotary magnet R which steps the wipers on to the next set of bank contacts. When an idle trunk is found, switching relay H energizes over its lower winding in series with stepping. relay E and switches the speaking conductors through to the next switch, earth being fed forward over the test wiper p Should all the trunks in the selected level be busy the wipers will be rotated to 11th contact position and operate the cam springs CS and OS on the 11th rotary step, whereupon the following circuit will be completed: earth will be connected to wiper p by the operation of the cam springs CS to operate an overflow meter (not shown). Springs CS will disconnect the vertical magnet V and connect earth to the negative speaking conductor. The connection of earth to the negative speaking conductor by the cam springs CS will operate the relayF in the battery feed selector over the following circuit: earth, CS 57, negative speaking conductor, negative wiper, 41, 15, 10, 43, lower winding of relay F to battery. Relay F upon energizing completes a locking circuit for itself and connects up the busy tone and busy flash conductor 18 in the manner previously d scribed in order to transmit a busy tone or busy flash to the calling party. The busy relay F also disconnects at armature 25 earth from the wiper p thereby removing earth from the release trunk conductor RT of the second selector, Fig. 2, whereupon the switching relay H which was partially operated now restores and closes the following circuit for release magnet Z: battery, Z, N 53. earth. From the above it will be seen that in the event of an intermediate selector finding all lines busy that the intermediate selectors are automatically released and the busy tone or flash trans magnet is as follows: negative speaking 'conmitted to the calling party from the battery :te'ed selector.

Assuming now that the intermediate selector Fig. 2, finds an idle line: Under these conditions there will be no earth on test wiper p and switching relay H will operate over its lower winding in series with relay E and switch through to the final selector, Fig. 3. By the operation of armature of relay H earth on release trunk conductor ET is fed forward over the wiper p to the release trunk conductorltl and operates relay X. Relay X upon operating opens a point in the circuit o'l release magnet Z and prepares a holding circuit for the final selector. "When the calling party dials the next series of inipulses, relay A or the battery feed selector repeats the impulses over the negative speaking conductor and the first vertical impulse is transmitted to the vertical magnet V of the final selector over the following circuit: earth, 1, 35, 5, C, 14, 39, 15', 41, negative wiper, negative speaking conductor, 57, negative wiper, negative speaking conduct-or, 78, V N N normally closed contacts controlled by 63, relay C to battery. Upon the first vertical step the off normal springs N, N open and N makes contact with its working contact and subsequent impulses are transmitted to the vertical magnet V over the following circuit: negative speaking conductor, 7 8, V rotary off normal springs NR 63, C, battery. The vertical magnet V sets the switch wipers opposite to the desired level and at the end of the series of impulses relays C, in the battery feed selector and C in the final selector de-energize. The de-energization of relay C will have no effect at this time but the de-energization of relay C will prepare the impulsing circuit for the rotary magnetR When the calling party dials the last digit of the wanted number the first impulse is transmitted to the rotary magnet R over the folowing circuit: negative speaking conductor, 7 8, R NR and its resting contact NR, and its working contact, normally closed contacts controlled by armature 63, relay C to battery. The rotary magnet new steps the wipers on to the first set of bank contacts in the selected level whereupon the rotary oil normal springs NR NR operate and the circuit for subsequent impulses to the rotary ductor, 78, R NR NR armatures 63, relay C to battery. Responsive to the impulses transmitted to the rotary magnet the wipers are rotated on to the deslred level of contacts and at the end of this series of impulses, relay C and C de-energize. Relay C upon deenergizing opens the impulsing circuit there by preventing any further impulses dialled by the calling party from becoming effective. Should the wanted party be engaged there will be an earth potential on test wiper p and under these conditions, the following circuit will be completed for the lower winding ofand busy flash to the incoming positive speaking conductor as previouslydescribed. Relay F also removes earth from the release trunk conductors RT and BT thereby re- I le'asingthe train of switches. hen earth is removed from RT, relay X die-energizes and completes the following circuit for release magnet Z earth, 61, N, Z battery. 7

If the called partly is free when a connection is established, relay H will operate over its upper winding in series with the switching relay of the wanted partys line switch and complete a locking circuit at armature 75 over its lower winding. Switching relay H also connects earth to the test wiper p at armature 73 to busy the called partys line and at armatures 7 2 and 77. connects up ringing current from the ringing machine GEN to the negative and positive speaking conductors as follows: positive wiper, 7 2, 65, upper winding of ER to interrupter ringing current and from the negative wiper,'77, resistance r to battery. 7

hen the called party answers,.relay BR operates and locks up at armature 67 and at armatures 65 and 71 connects up the positive and negative speaking conductors to the wanted line, battery being ted to the calling partys line through windings of the A relay in the battery teed selector, Fig. 1, and to the called party as follows: earth, at armature 17 of relay Q, winding of relay G, 9, 36, 6, positive speaking conductor,'-and battery is connected to the negativesp'eaking conductor from battery, lowerwinding of relay F, 43, 10, 15, 41, negative speaking conductor. .Relays F and G operate over the called partys loop, but the busy circuit will not be completed since relay G is quicker to pull up than relayF and relay G opens. the busy circuit at 29 before armature 47 of re lay F operates.

Relays G and F also complete the following circuit for reversing relay D: battery, D, 33, 27, 10,15, 41, negative wiper,'called partys loop, positive wiper, 6, 36, 9, G, 17, earth. It will thus be seen that relay D is connected in parallel with the lower windin of relay F; Relay 1) upon energizing disconnects the lower winding of relay F at armature 43 and maintains its circuit through 33, 43, 10, 15, 41. to the negative wiper; Bat

tery for talking purposes is now fed to the called party through the winding 01 relay l) to the negative line and earth to the positive line through relay G. Relay D also reverses the direction of current to the calling line to o )erate a meter or other supervisory device.

It may be mentionec. here that a bank contact such as 60 is engaged by the wiper p on all levels having access to local switches, the bank contact such as 59 which is connected to earth being engaged only on the levels having access to trunk lines leading to other exchanges. Consequently since bank contact 60 is left dead, relay Q will not operate on local connections.

A description will now be given of the operation of the battery feed selector, Fig. 1, in extending calls to distant exchange. The battery teed selector operates in the manner previously described for the first digit but on the level or levels having access to interexchange trunks, the relay Q, is operated over wiper 2?. Relay Q, upon operating connects at aru'iature 17 the high impedance relay G and the right hand winding of the polarized relay P across the outgoing positive and negative speaking conductors, the circuit being as follows: negative speaking conductor, 2, right hand winding of polarized winding p, 17, G, 9, 38, 6, positive speakconductor. Relay G at armature 18 closes i so that relay A will transmit loop impulses to the distant exchange, the circuit being: negative speaking conductor 2, 18, 6, positive speaking conductor. The springs r A control the loop circuit across o and negative speaking conducav Q at armature 1e disconnects .n the vertical magnet V and conir to battery through the resistance r armature l2 prepares a circuit for a sitting the busy flash and tone to the incoming positive speaking conductor.

ii, the end of the impulse transmission, re-

will tie-energize and the switches in no distant exchange will be held over relay d the right hand winding of relay P. any (,1 is also arranged to change over the connection from the intermittent busy lead ill to a continuous busy lead CB since relay Q. is operated over the test wiper p and a i contact in the second selector bank. It will be readily understood that trunks leading to distant exchanges may be taken from the levels of any subsequent selectors the particular place at which they extend to distant exchanges being determinedby ear-thing the bank contact engaged by the wiper p at that particular switch.

1f the called party is busy when inter-exchange connections are set up, the high impedance relay G will be released and operated by the busy conditions at the distant incoming selector and will connect up a busy tone or busy flash signalling current at the battery :teed selector, Fig. 1 to the calling subscriber or operator as the case may be. The contacts 29 relay G will repeat the busy tone and busy flash over the following cir-- cuit: continuous busy tone and fiash leads CB, 13, 29, 12, 7, positive speaking conductor. l/Vhen the called party answers, battery is reversed at the distant ofl'ice-over the outgoing speaking c-onductors and the polarized relay P operates and completes an energizing circuit for relay D at armature 20. Relay D upon energizing reverses the direction of current over the incon'iing speaking conductors tor metering or supervisory purposes, battery being ted to the calling party from relay A and to the called partly from the distant exchange.

The release of the connection is under the control of the calling party since relay A controls relay G at armature 2 and relay G in turn controls relay H, the release magnet circuit being as follows: battery, release magnet Z, at), N, 5, 35, 1, earth.

hat I claim is 1. In a telephone system in which connections are set up through a first selector having a directed group-selecting movement and a tree trunk-hunting movement to select an idle trunk in the selected group and an intermedi ate selector having similar move ments, primary magnets in said switches, respectively, for eitecting the group-selecting movements, a line relay in the first selector arranged to repeat impulses directly to the associated primary magnet and to repeat lll1- pulses over a talking conductor directly to the primary magnet of the intermediate selector after such selector has been taken into use, and means associated with said first selector for exercising a control over the other talking conductor at the end of the group of impulses transmitted to the intermediate selector so as to cause said intermediate selector to initiate its free hunting operation.

2. in an automatic system in which connections are set up through trains of switches each containing a selector having a directed group-hunting movement and a free trunk hunting movement, said movements being controlled by a. primary magnet and a hunting magnet, respectively, circuit arrangements for transn'iitting impulses directly to the primary magnet of an intermediate switch over one talking conductor of a connection established thereto, and separate circuit arrangements for exercising a control over the other talking conductor so as to cause said intermediate selector to initiate its trunk-hunting movement at the end of the group-selecting movement.

3. In a telephone system in which a con nection set up from a calling line to a called line includes a first selector repeater and a plurality of other switches, means in the first selector repeater effective when one of the other switches finds all trunks in a selected 'roup busy or finds the called line busy for releasing the other operated switches in the train and for transmitting a busy signal to the calling line, said means being controlled over a circuit path including one talking conductor of the established connections and excluding the other.

4.. In a multi-exchange telephone system in which connections are set up through a plurality of selectors in serial relation, means associated with the first selector of a train and eliective in local connections for repeat ing impulses to the succeeding switches involved in the connection over a circuit includ-.

ing one talking conductor and excluding the other, and circuit arrangements automatically effective in case the connection-is extended to a distant exchange for modifying the control circuit so that impulses are transmitted to the distant exchange over the two talking conductors in series.

5. In a telephone system in which conncctions are set up through a first selector repeater and through a plurality of other switches in serial relation, means associated with the first selector repeater for causing it to repeat to the other switches impulses different in one case from the impulses repeated in another case, and controlling means governed in accordance with the value of the series of impulses controlling the operation of the first selector repeater for determining the nature of the impulses repeated by the first selector repeater.

6. In a telephone system as claimed in trolled in accordance with the position in which the first selector repeater is set.

8. Ina multi-exchange telephone system, means including a train of automatic switches for setting up a connection from a calling line in one exchan e to a called line in the same exchange and including the first switch of the train for setting up a connection from said calling line to a called line in another exchange, circuit arrangements associated with the said first switch for supplying talleing current to the calling line in each case, and for supplying talking current to the called line only in case the called line is a local line, a supervisory-control device associated with said selector repeater operated in response to the flow of transmitter current when alocal connection is set up, and means for operating said device responsive to a reversal in the fiow of current when the called subscriber responds in an inter-exchange connection.

In testimony whereof I have signed my name at Liverpool England, this 24th day of June, 1926.

NliLLlAM OGLESBY PASSMORE. 

